Setting Up Your Environment

Clojure development revolves around an editor connected to a REPL, so you can evaluate any expression with a keystroke.

Editor

• Visual Studio Code + Calva — the most popular free choice. Calva starts ("jacks in") a REPL for your project, evaluates forms inline, and includes the clojure-lsp language server and structural editing.
• IntelliJ IDEA + Cursive — a full-featured Clojure IDE (free for non-commercial use).
• Emacs + CIDER and Neovim + Conjure — long-standing favorites of experienced Clojurists.

Structural editing

Editors for Lisps keep parentheses balanced for you (paredit or parinfer): you move, wrap, and split whole expressions instead of typing brackets by hand. Learn a few commands early — it makes the parentheses disappear from your attention.

Linting

clj-kondo (built into Calva and clojure-lsp) finds unused bindings, wrong arities, and typos as you type.

Starting a REPL in a terminal

$ clj
Clojure 1.12.6
user=> (+ 1 2)
3
user=> (str "Clojure" " rocks")
"Clojure rocks"
user=>

Press Ctrl + D (or Ctrl + Z then Enter on Windows) to quit. The plain terminal REPL is fine for a quick try; for real work, use your editor's REPL connection.

A minimal project

hello/
├── deps.edn          {:deps {}}
└── src/
    └── hello.clj

Run it with clj -M -m hello (Level 3 explains deps.edn and -M).